US2190540A - Printing telegraph system - Google Patents

Description

Feb. 13, 1940. J. M. DEsMoND 2,190,540

PRINTING TELEGRAPH SYSTEM Filed April 6, 1938 5 Sheets-Sheet 2 POLAR/ZID TWX OFF/CE B 1 `l" @Lf J. M. DESMOND PRINTING TELEGRAPH SYSTEM Feb. 13, 1940.

Filed April e, 1938 s sheets-sheet s im, w.

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/N VEN TOR B VJM. DE SMO/VD l 2 l n A Tron/v5 y l J. M. DEsMoND 2,190,540

PRINTING TELEGRAPH SYSTEM Filed April e, 195s 6 sheets-sheet 4 Feb. 13,1940.

Fe E3 l4 J. M. QDEsMoND l I PRINTING TELEGRAPH SYSTEM Filed April 6, 1938 6 Sheets-Sheet 5 #.0 INTER VAL l-5 /N TERVALS 7- n Lamine-Lease 'ATTORNEY Feb. 13, 1940. J. M. DESMOND 2,190,540

PRINTING TELEGRAPH SYSTEM Filed April e, v19323 e sheets-sheet e A yFIG. l0,

o/sco/vA/Ecr RECALL WE/v TOR J. M. DE SMOND By A L@ Lm'../IIMAMSJ ATTORNEY Patented Feb. 13, 1940 IUNITl sr rientrino restanten SYSTEM i James Michael Desmond;v Great Neck, N; Y., as-

signor to American Telephone and Telegraph Company, av corporation 4of Newi York Applicationy April 6, 1933, Serial N0. v200,542 7 ilairns.` J(Cl 178;.;2)

This invention relates to printing telegraph` .L systemsnand moreparticularly to signaling ar-v rangements adapted for use-therein. v

An object of the invention is to reduce the time required for transmitting supervisory signals in l printing telegraph systems. A more Specific object is to. employ permutation code combinations of electrical current impulses `for exchange system. l,

toll trunk signaling arrangementsthe method of .transmitting supervisory signals over trunk circuits betweenteletypewriter exchanges,v em- `onds Afor a recall signal, and nine to ten sec-` onds for a' disconnect signal. VThe purposeof thecall, the recall ,and the disconnect signals is f fore supervisory signals wereoccasionally operl.

ated by mistake. Furthermore,3 the x length of time required to send recall and disconnectsig- 1 30 nals as heretofore accomplished is considerable,

particularly in cases where the signaling isl eX#- tended over twoor more toll or, trunk circuits;

According to the present inventionthe transeighth` and Vninth selecting impulses of each code A, mission of the supervisory signalsI is effected by means of a motor driven signaling device which is separate from the regular` message printer set and which may be located at a point distant from the operators switchboard position. The device ,is of the start-stop type larranged `to, transmit current `impulses in permutation code combinations. lit uses a code which diers from the standard five-units start-stop teletypewriter.

l `code in that it uses fourteen units 'consistingV of .l

Qastart pulse, twelve selecting pulses and Aa stop 1" pulse. `,CJombinations of the twelve selecting impulses when transmitted overa line circuit, are

[respectively eiective to operate a call, a recall,

and a disconnect signal at the receiving end ofv the circuit. Twelve ofthe fourteen pulses are rj ixed Vand two are changeable for selectin-g puroperating supervisory signalsin a' teletypewriter v j transmitted during leach unit` interval. Heretofore in teletypewriter exchange inter `'for each `oi the supervisorysignals.

ployed timed open signals, for exampleone to two seconds for a call signal, six to eight seci standardve-units start-stop teletypewritenor 'message code device. The device comprises four segmented `cam-,operated contact sets, one to v transmitthe fixed intervals and close the line circuit during the idle period, one each for ther` 5 two changeable intervals and one for locking and releasing purposes.V `The cams are provided with different arrangements of cuttings depending on `the type of signaling current impulse thatis ThreeillO l keys arefprovided at the operators position, one

One receiving unit is required for each transmission line and one transmitting unitfor each operators position. Transmission units for two or more* 5 operators positions may-be driven by a common shaft.v At the' receiving Vendthe line circuit is connected-throughthe windingV of a polarizedl relay arranged to operate, through auxiliary app-aratus, a selecting magnet on a special printer 20 located at a point remote to the receiving operl ators position andindependent of the message receiving printer set at the subscribers station or the operators printer set. The selecting magnet `and the selector, mechanism of the spef cial printer is substantiallyy that of the printer disclosedin U. S.- Patent`1\,' 745,633 granted to S.` Morton et al.` on February 4, 1930, except that the spacing signal impulses are eie'ctive to op- -erate contact sets insteadof the marking signal- 30 impulses selecting code bars. 'I he selector ."mechanism comprises four cams arranged to be respectively responsive vto the sixth, seventh,

combination `or signaling impulses transmitted' 35 from the other endof the lineicircuitand there- The .Contact setsgoperated in different ,combina-l.` 40 tions are effective to select and operate the call,

the yrecall or the disconnectsignal as desired.

The invention will now'berdescribed in 4oon-- necton withthe attached drawings n which:

,"F'igure l. is aschematic,` representation of 2.,.45

teletypewriter lexchange System wherein the `supervisory'signaling devices at the transmitl ting tendaoi the-trunk circuit are shown individual to `.the `cord circuit Vand the supervisory l sig-nali receiving devices are shown individual to,A 50

tnetrunk circuit; `1 lFig. f2 isa diagrammatic arrangement showingy the relation between two 'revolutionsof the standardfive-lmits code start-stop .distributor and one revolution of thepecial transmittingT55v supervisory signaling start-stop distributor having fourteen unit intervals, the special distributor being equipped for three diierent signaling impulse combinations;

Figs. 3 is a relative arrangement of Figs. 4,. 5 and 6;

Fig. 4 shows a subscribers station A in schematic form terminating at teletypewriter exchange office B, the termination'being made at an y Fig. 6 shows trunk line equipment at teletype-l writer exchange oiiice B and also at teletypewriter exchange oiiice C the trunk line and trunk line equipment comprising the special supervisory signal receiving device and assocated equipment, a universal cord circuit connected in multiple to a diagrammatic representation of an operators switchboard position similar to that shown in Fig. 5, and a lsubscribers line equipment, and at station D a subscribers teletypewriter set in diagrammatic form;`

Fig. 7 represents a superimposed arrangement of the signal transmitting cams employed on the signal transmitting device shown in Fig. 5. The arrangement presumes that the four cams arev placed coincidentally on top of each other, and

shows the angular widths of the fourteen seg- 'Y ments for measuring the fourteen intervals;

Fig. 8 shows the four cams of the signal transmitting device and their respectively associated y contact sets caused to be operated by the cam cuttings. These cams are shown superimposed on veach other in Fig. 7;

Fig. 9 represents a superimposed arrangement of the signal receiving cams employed on the signal receiving device shown in Fig. 6. The arrangement also presumes that the fivecams are placed coincidentally on top of each other and shows the angular widths of the fourteen segments corresponding to the fourteen meas- 4 uring segments of the signal transmitting device;

Fig. l() shows the six cams, namely, the start, four selecting and the `stop cams of the signal receiving device and their respectively associated contact Sets caused to be operated bythe f cam projections which are located approximately in the middle oi the sixth, seventh, eighthv and ninth segments of the successive cams of the selecting group.

Referring to Fig. l, means are shown for connecting subscribers station A to subscribers station D over any one of a plurality of trunk circuits til, respectively designated tilt-I, ttm-2, {itil-3, etc., and extending between v switchboards respectively located at teletypewriter ofce B and teletypewriter office C. Each of the trunk circuits is multipled to a plurality of switchboard positions at each of the teletypewriter ofces, the trunk multiple being shown, in Fig l, as connected to two switchboard positions at `each of the teletypewriter exchange ofces.v A plurality of cord circuits, such as that nated 5d@ and the device designated 59|.

ce B and that designated GEH at teletypewriter exchange oftce C are provided at each switchboard position. Common to the cord circuits at each switchboard position at teletypewriter exchange oiice B are a teletypewriter set and a signal transmitting device, the set being desig- Likewise, common to the cord circuits at each of the switchboard positions v at teletypewriter exchange oillce C are a teletypewriter'set and a signal transmitting device, the set being designated i592 and the device designated 03. The teletypewriter sets are of the standard five-unit code` transmitting to a distant station or oiiice, a call,

a recall, or a disconnect signal depending on which one of the three keys is operated. Located` at each of the teletypewriter exchange ofces isa specal type of signal receiving device for each of the trunk circuits incoming at the cfce. At teletypewriter exchange oice B the trunk circuits SD-i, S-2, G60- 3, etc., are respectively connected to signal receiving devices 'lfi-l, Nfl- 2, lull- 3, etc., and at teler,typewriter exchange ofoe C the same trunk circuits are respectively connected to signal receiving devices Stil-l, 604-2, 5ml-3, etc. The signal receiving devices at each of the teletypewriter exchange omces are individual to the trunk circuLts and each is responsive to a fourteen-unit code transmitted from the signal transmitting device that happens to be connected at the distant oliice to the trunk circuit associated with the responding signal receiving device. The signal receiving device is adapted to close in response to a supervisory signal transmitted from the distant office, any one of the three combinationsof contacts which close a circuit for operating the desired signal lamp at the receiving office. A detail description of the operation of -the signal transmitting and signal receiving devices will be hereinafter given.

Fig. 2 is the diagrammatic arrangement showing the relations between two revolutions of the standardr ve-unit start-stop distributor and one revolution of the signal transmitting device, or distributor, which provides twelveselecting intervals, or units, and two synchronizing intervals, or units. The speed of the signal distributor showing the three combinations of signal impulses, namely for the disconnect, the

recall and the call signals, is one-half of the standard 60 speed distributor shown at the top of Fig.v 2. Each interval, or time unit, of the signal distributor is one-half the length of each unit oi the standard distributor. The line speeds oi the signal intervals are-equal to those of the standard interval and one revolution of the signal distributor will equal, in time, two revolutions of the standard distributor.

In the distributor arrangement shown, units designated by Ia dash line indicate either the closed or open interval, that is, marking or spacdesignated Lilli at teletypeWr-iter exchange of- N ing signal; a full, or solid, line indicates a closed,

the standard .distributor there are seven intervals. Thecfirst intervaltransmitted in arevolution` is always spacing 'and the last interval is always marking. In the signal distributor there are fourteen intervals. The first interval is f always spacing and the last interval is always yvof consequence as far as 'the operating intervals are concerned. For example, for transmitting marking, `but the seventh interval corresponding to the last interval of a standard distributor is always spacing and the eighthvinterval ofthe signal distributor corresponding to the first interval of a succeeding revolution of a standard.' distributor is always marking.

The signal distributor may be connected to a standard `60 speed line circuit and will operate, but will not notselect onlthe standard 60 speed signals. If only one standard 60 speedrevolution is transmitted, the situation in the signal distributor will not be materiallychanged. i j

.The code selectedfor the call, the recall and the disconnect signal operations were chosen for simplicity of illustration and incorrect operation'y may be further minimized by using .more of the` selecting intervals available. Operation ofthe receiving signal distributor on all standard 6()` speed signals is avoided by introducing a slowacting relay adjusted so that it will not operate on the longest standard 60 speed spacing signal,

namely, the' letters, but will operate on a spacing signal of slightly longer duration. In the codel arbitrarily selected for the proposed arrangement twelve o'f. the `signal intervals are fixed and two are changeable. Cam-operated contacts are proposed for the signal transmitting distributor, one to transmitthe fixed intervaisand j close the line circuit during idle periods, one each for the two changeable intervalsandone for locking and releasing purposes. Itv will be noted in the diagrammatic showing `of the signal distributor in Fig. v2 that the changeable intervals,`

that is, the sixth, seventh,`eighth and ninth, are

the receivingy oice. The operation of the disconnect, the recall and the call key at the transmitting operators position selects the. signal combination to be .transmitted and the four sets of contacts at the receivingA oflice `operate accordingly in the desired combination to close a circuitextending to the disconnect, `the recall, the call signal lamp depending,` on the signal im- 5 pulse combination transmitted.

l Method of'opcmtion-Cord circuit `Referring toFigs. 4, 5 and 6 the operation of the system will nowbe described. Assume that a subscriber atstation A, shown in diagrammatic form, originated a' call in the usual manner and that the operators at teletypewriter exchange offices B and C'have, in response to such call and inA turn, established a connection by means of their respective cord circuits, such as cord circ-uit 4011 shown in detail` andcorcl circuit Gili shown 1n If all four intervals are employed for` station D] also shown in diagrammatic form.

Subscribers stations A and D, together with their respective line circuit equipments (not shown) at the teletypewriter exchange oices maybe of the typedisclosed in U. S. Patent 1,965,383 granted to `diagrammatic form, throughto the subscribers C. C. Lane onJuly 3, 1934. Cord circuits #till and tu! are ofthe universal type Well known in the art. A brief description of the operation of cord circuit liti when first, the answering plug of the cord circuit is inserted in the calling line jack in response to a call and then the calling plug is inserted` in the trunkl jack, will now be given. The subscribers stations, the station line equipe ments, the cord circuits, the toll line and toll line equipments form no part of the present invention and therefore only such parts.` of them willy be described as seem sufficient to establish a connection. A brief description of the connection is deemed necessary in order to present a system `wherein the novel features of the invention,

namely, the supervisory functions :fory an intertoll teletypewriter exchange system may be satisfactorily described in detail. For a clear understanding of the operation'of the system, set forth `above as not forming a part of the present invention, re-ferencemay be made to the copending. ap-

tions of the switchboard in which-the jack ac3 vis located. A circuit is closed :extending from ground,through the winding of a relay in the line` circuit equipment (now shown), the sleeve conductor of jack 433 and plug 11GB, through the v'lower winding of relay litt, through the winding of relay` 4G13 to a potentiometer consisting of resistances lill and 568. If this cord circuit is the rst to complete the sleeve circuit?, the midpoint U of the potentiometer will be negative with respect to the sleeve and relays M55 and` :itil will operate and apply ground located at the armature of relay 40, to the winding of relay fiile, thereby operating it. Relay i305, in operating, closes a circuit extending from grounded negative battery, through the winding of relay diie, innermost upper armature and Contactv of relay M35, through the upper Winding of relay d66 to ground on the sleeve conductor of plug 4t2 and jack 03. rlhe circuit last traced will constitute a lockingcircuit for relay 413B and the operating circuit for relay 499.

li another answering cord has preceded this4 cord into the multiple of the line, the sleeve will be negative with respect tothe niidpoint of the potentiometer and thepolar relay it will not operate.M This non-interferingy feature is described inthe copending application of iocke et al, supra, `Relay #it will operate` closing a circuit extending from ground on the armature and right-hand contact of relay litt, contacts and lower armature of relay 4M, through the winding Relay t of relay lill to grounded negative battery. lll, in operating closes circuit `extending .from grounded positive battery l5 I, conductor 592', armature and contact of relay t l il, ring conductor of plug 402 and jack 463, over the line multiple to the ring of the preceding cord. If the teletype- `writer'keyof the preceding cord is ope1ated,.the

preceding operators set will be cut through andA positive battery on the ringwill shunt downa relay in the preceding operators set circuit which will c-ause that operators teletypewriter to lock up so as to be inoperative during a double plug-in condition. The interfering operator will not receive an indication of a double plug-in condition until she operates the associated typing key.

' Since the ring is opened the operation of the typing key Willcause a relay in the operators set circuit to release, which in turn, causes the operators busy lamp 505to light. The operators typing key is designated 4l l in Fig. 4. The operators teletypewriter will run open momentarily and then lock up and the keyboard will be inoperative. Care should be taken to avoid operating the typing key of an idle cord circuit as this will cause the busy lamp in the operators set circuit to light. Upon receiving the busy lamp signal, theoperator should remove the interfering cord. This will allow the preceding operator to proceed with the call.

However, it is usual that the interfering operator make a busy test before inserting an answering plug as is well known in both the telephone and telegraph art. This busy test is made as follows: Polar relays 592 and 5% of Fig. 5 are associated with the tip conductor of each of the cord circuits in the operators position, through the contacts and armatures of sleeve relays, such as relays 404 and 465 at the answering plug U2 or such as relay 5 l 2 at the calling plug 489. When the cords are busy, relays 502 and 5&3 are disconnected by the operation of the sleeve relays 464 and M35 or sleeve relay 462. When the tip of either of plug 402 or H89 is touched to the sleeve of any one of their respectively associated jacks, that is, a line jack or a multiple thereof of a busy line or trunk,y grounded negative battery (not shown) which will be connected to the sleeve of the particular busy jack, completes a circuit eX- tending through the winding of busy relay 502 to ground. Relay 5&2 operates to thereby connect ground to the conductor `extending to the grounded battery through the lamp 505 which lights to indicate that the line connected to the particular jack is busy. Relay 5&3 being polecl for operation from grounded positive battery does not operate in response to a busy test.

The out-of-order test which like the busy test is also well known in the telephone and telegraph art, is made as follows: When the tip of either end of any cord in an operators position is touched to the sleeve of a jack in whose multiple there is a jack wherein an out-of-order cord is inserted, grounded positive battery (not shown) l, lwill be impressed on the sleeve of all jacks of the i multiple of the out-of-order line whereby a circuit is completed extending through the winding of relay 5% to ground. As stated above, relay 593 is poled to operate from grounded positive battery and relay 503 operates to close a circuit extending through the winding of an alarm relay 558, through busy lamp 505 to grounded battery. Lamp 595 lights to indicate an engaged condition. The alarm relay operates to connect a continuous ringing current through lamp 55! to a buzzer 552.

Lamp 55! flashes and buzzer 552 operates to indicate an out-of-order condition and therefore diierentiates from the busy condition indicated by the lighting of lamp 585 alone.

The operation of relay M36 as hereinbefore described closed acircuit extending from ground over. the armature and left-hand contact of relay. d66, conductor M2, through the left-hand winding of relay 452 to grounded negative battery and relay 452 operates. Relay 452 in operating applies at its right-hand armature ground for the balancing network 353 and at its inner left-hand armature and contact, ground for the balancing network 45d, the balancing network being furnished for the satisfactory operation of the repeater. Relay 452 will operate when either or both the calling or answering ends of a cord circuit are inserted in their associated jacks.

After the operator inserts the answering plug in the line jack, the circuit from the answering side ci the repeater to the ring conductor of the answering plug 02 is closed and may be traced from grounded negative battery in the station line circuit equipment (not shown), ring conductors of jack M3 and plug M32, make-beforebreak contacts of relay 5635 in an operated position, conductor lill, conductor M4, outer upper armature and back contact of relay 4l3, resistance 62?., conductor d5?, through the upper Winding of repeating relays 55, armature and right contact of repeater relay @t4 to grounded positive battery. A second path extends through the lower winding of relay 555, network B54 to ground at the contact and inner left armature of relay $52. The biasing current flowing through the lower winding of relays M5 tends to operate the relay armature to the left contact, but the current flowing through the upper winding predominates and the relay armature remains ln engagement with its right contact.

'The typing keys and relays are so arranged that the operators teletypewriter set may be connected to any cord in the immediate position and where teamwork is furnished at the operators switchboard, the operators teletypewriter set may also be connected to a number of cords in either of ythe two adjacent positions. However, the arrangements shown on the drawings Vdo not show any provision for teamwork.

. `When a typing key, such as key ail, in the operator-s position is not operated, a line relay 6536 of the operators position circuit will be operated to its left-hand contact by virtue of a holding current which flows in a circuit extending from ground through thelower winding of th-e relay, closed right-hand contacts or" the battery key 553 to a point in a potentiometer including the grounded negative battery at the lefthand contacts of the battery key and the grounded positive battery connected to the winding of the slow release relay 55d. Printer magnet SI2 is normally held energized by current flowing in a circuit extending from grounded positive battery, armature and left-hand contact of relay i, through the winding of magnet 512, leithand closed contacts of the battery key to grounded negative battery. The holding current prevents the teletypewriter running open during the idle condition of a transmission period.

When the operators position typing key lll is operated a circuit is closed from ground through the lower winding of relay 586, conductor t5?, closed contacts of the teletypewriter key, conductor M8, make-before-break contact of relay li in an unoperated position, through the winding of relay di@ to grounded positive battery to form a circuit with the potentiometer hereinbefore described, thereby maintaining a biasing circuit extending through the lower winding of relay 586. Relay fili) operates and closes at its inner left armature and contacts a path extending through the winding of relay H3 to grounded positive battery. Relay i3 operates and closes at its lower armature and contacts a lholding circuit for Arelay 4|9. Also, relay M3,

in foperating; closes at itsinner upper .armature and Vi'ront contactan'obvious circuit for operaty ing slow-'acting relay 429.* A communication circuit is now closed extending from grounded nega- :tive battery atthe subscribers station line equipment, not shown, ring conductors of jack Mit and plug tut., 'make-'beore-b-reak contact of relay Mill in an operated position, vconductor d il conductor 4I li, contact and outer .leftarmature of relay willig, 'conductor 425, through the operators telelbperators set.

typewriter set Mill,` through the ,upper winding ofzpolarized relayti, conductor 55,"armatures and their respective back contacts, in series, of

relay Elli, conductor 5H, outer right armature :Band contact of relay M9, conductor d5?, and as hereinbefor-e traced to grounded positive battery at the right contacts of relay 464 in one path andto ground at the inner leftarm'ature and contacts of relay 452 in the other path as hereinbefore traced. However, should it be desired, for

some reason,that the typing key 4I! berestored to normal at this time, relay M3 would release before relay MS, and resistance 422 would be replaced in the circuit'between the ring conductor Lof answeringv plug 15u12 and the Winding of repeater relay dtbefore the operators teletypewriter set is disconnected. This is done to insure that the `transmission through the repeater will' .not be `interruptediby the lintroduction or lremoval of the operators set.

The line relay 5535 'at the operators teletypewriter set isnormally held closed by a local negative L,iS-volt circuit'and the printer magnet 5l2 is held operated kby another local circuit from negative 34-vcltbattery. Current through the `conductor ll'lvis applied to the biasing winding of the operators set line relay 506 in the direction `opposite 'to the local holdingfcurrent. This current'in the conductor 5411 `is greater than `the local current and will therefore act as a biasing current for the operation of the `line l relay.. When the `typing key fill is operated, the subsequentoperation of relays H9 and Mphereinoefore' described, might cause a sufficiently large current in conductor 5B1' to over-power not` only the local holding current, but the line current as well.` If the printer magnet 5I2 were undercontrol of the line relay 595 at this time, falsecharacteristics might be recorded in the This condition is prevented by the fact thatthe second local circuit in the 0perators set holds the `printer magnet closed until relay A25) operates. Relay 429 which is slowacting will operate when relay M3 has operated Wand will then supplyfground through conductor rll'igilower armature and contact of relay 23, contact and inner right'armatureof relay dill, conductor ttthrough' the winding of relay M3 to' grounded battery. Relay M3 operates and thereby opens the second holding circuit for relay `magnet l. When typing key .dit is 1restored to normal the biasing current for `the operators `linerelay will be opened and the local holding current will be established before 7the line circuit is opened;

In a case where two operators attempt to answer the same call, both will be prevented from accepting the call and will be informed of the double connection by signals. The first oper- "ator who completes the sleeve circuit of an answering cord: will have her teletypewriter locked asV an indication. The'second operator will ree ceive a busy lamp signal in herposition and will have her teletypewriter;locked as an indication.

.The second `operatormay `disconnect and the aff rst operator .may proceed with the business of 1 answering the call. The circuit arrangement for performing this operator lock-out feature at the second operators position comprises a relay 506 which because of the discriminative eaturein the cord sleeve circuit at this time prevents closure of the transmission circuit, is operated y to its spacing contact. Relay 505 is operating:

to its spacing contactreleases relay 65d without eiiect and causes the second holding circuit of printer magnet 512 to be energized sumciently to holdthe magnet operated, the latter circuit being traceable from grounded positive battery of i 48 volts through the winding of relay 555, make-W before-break contact of relay 513, throughthe winding of magnet 512 to grounded negative battery oi 48 vvolts vat key 553. Relay 555 op# crates to light busy lamp il'ii. The lighted busy lamp Edili and the locked teletypewriter indicate tothe second operator that her position is locked outV of the line circuit and that she should disconnect. Relays 554, 555 and lili), printer magnet" l 512, key ifand busy lamp 595 correspond respectively to those parts similarly designated in Fig. 5 of the drawings.

Whenthe operator at teletypewriter exchange oce B challenges the subscriber at station A; i relay 5% will respond to the teletypewriter signal by virtue of the signaling4 current in `the upper winding of relay 506 which current is apso w11 proximately twice thatofth'e biasing currentin the lower winding ofthe relay. Relay 5% re-` spending to the teletypewriter signals will in turn operate the printer magnet M2. is normally energized when the battery key 553 is operated and being of the slow-release type remains operated during `the message signaling but is shunted and therefore releases when `the armature of relay 5&5 remainson its spacing, or-

right, contact. Relay lila operates in a circuit traceable over conductor 132 extending tofth'e associated cord circuit overthe inner right ararmatureand contact of relay 452, when the answering plug to2 isinserted into line jack 483,

the calling line will not operate because ymature and contact' of lrelay M9, Contact and` armature of relay A28' to ground at the outer left v Y intertoll trunk jack for "an idle condition and if the trunk is idle then insertsy the calling plug 489 `of cord circuit til! into an intertoll trunk jack indicated as idle by the 4idle line indicator, lamp tdwhich intertoll trunk jack is shown in the drawings as being jack 505. The normally closed l intertoll trunk circuit is arranged to remain closed during the time that plug 89 is being inserted into' jack 60E. When calling plug 489 is in jack SDE a circuit is completed from ground which is present on the sleeve of they jack and eX- tends through the sleeve of plug 1383., resistance t'lll, through the winding of relay li/ll togrounded battery. Relay till operates and at its lower armature connects ground in an obvious `operating circuit for relay 462. and completes a circuit from 'grounded negative battery in the toll line equipment (not shown) Relayv Q62 operates.

ture of relay 452.

keys designated c, r and d.

v ing distributor 50|.

at teletypewriter office B over the ring conductors ture and right contact of repeater relay l155 to grounded positive battery. A parallel path extends through the lower Winding of relay ,564, network 453 to ground at contact and right arma- Relay 462, in operating, also disconnects the tip conductor of plug 589 from the tip busy test conductors 415 and 504. The equipment at teletypewriter exchange ofce C is well known in the art and a description of it may be had by referring to the copending application Serial No. 459,684, supra.

As soon as plug 489 is inserted in jack 605, the operator at the teletypewriter exchange oflice B sends a call signal to the operator at the teletypewriterexchange oliice C, the typing key M being in an operated position at this time. The call signal is transmitted by the special printer, or distributor, shown in Fig. 5, which is part of the present invention and its effect on the equipment at the teletypewriter exchange ofce C will be hereinafter described.

'Ihe operator at teletypewriter exchange office C answers by plugging in the answering end of .a cord circuit such as that designated 60|, into jack 606, and challenges the operator at the teletypeiwriter exchange ofce B. The operator at teletypewriter exchange oflce B upon being challenged by the operator at the teletypewriter exchange oice C, transmits the code number of the called subscriber. 'Ihe operator at teletypewriter exchange oflice C will by means of the calling end of cord circuit 60| complete the connection through to the subscribers station B in a manner as hereinbefore described for completing the connection to the toll line. Now that the connection is established the func-- tion constituting the present invention will be described.

'I'he present invention, as hereinbefore. stated,

resides in the supervisory :function proposed for use between operators at teletypewriterexchange oiiices when operating over toll circuits. 'Ihe supervisory functions and equipments heretofore used at teletypewriter exchange oices will be used only for the subscribers stations that are local to the teletypewriter exchange offices, and inasmuch as they are well known in the art, they will not be described herein. In the arrangement herein described, `it is assumed that the operator at teletypewriter exchange omce B is sendingand that the operator at teletypewriter exchange oi'lice C is receiving. Each office is provided with three keys for intertoll office supervision. These keys at oflice B are shown as call key c, recall key r and disconnect d. As hereinbefore stated, the special printer is a modication `of the standard printer disclosed in U. S. Patent 1,745,633, supra, whereby the standard cam arrangement is replaced by the cam arrangements shownin Figs. 5 and 6. The cam arrangement in Fig. 5 is under the control of any one of the In neither of the cam arrangements shown in Figs. 5 and 6 are the type bars or code selecting bars, as used in the standard printer, employed.

Supervisory signaling equipment at oflice B which will herein be assumed to be the sending end, will first be described. There is associated with each of the operators cord circuits a signal- The signaling distributor and other signaling distributors such as that 1 indicated diagrammatically by box 5|4 are provided in the arrangement shown as being driven from a motor, through a common driving shaft 5|6. On shaft 5|5 is provided gear arrangements for each of the signaling distributors. 'Ihe signaling distributors are controlled by individual driving shafts Ell-A, 5Fl-B, etc., friction clutches 5MB- A, etc. and driven shafts 5| 9-A, etc. The signaling distributor 50|, shown in detail, will now be described.

Fixedly mounted on driven shaft 5|9-A are ve cams 525, 52|, 522, 523 and 524|, four of which, namely, 520 to 523, control contact sets. Cams 520 to 523 are shown superimposed in Fig. 7 and individually in Fig. 8. Cam 522 transmits the rst to the fifth, seventh, eighth, and tenth to the fourteenth interval impulses which are fixed, that is, unchangeable, of thel lll-unit code and also maintains the line circuit closed during idle periods. Cams 52| and 520 respectively transmit the sixth and the ninth interval impulses which are changeable. Cam 523 transmits no interval impulses to the line circuit but is employed for locking and release purposes. An additional cam 525 is not of the contact closing type but serves, together with friction clutch 5|8-A, to effect the starting and stopping operation of driven shaft 5|9-A- The operation of the signaling distributor 50| will now be described. Switch 525 is operated to its closed position to start the motor 5 I 5. Then the switchboard operator closes any one of the supervisory signal keys c, r or d, depending on the type of supervisory signal that is to be transmitted to teletypewriter exchange oflice C, and a corresponding sequence of circuits are operated. First, assume that call key c is operated to close the circuit extending from grounded battery through the winding of prepare relay 526, then over parallel paths, one extending over the left-hand contact of key c, through the winding of selector relay No. 6, designated 521, and the other extending over the right-hand contact of key c, through the winding of selector relay No. 9, designated 528, over a common conductor 529, through the winding of toll transfer relay 5I0 to ground. Relays 526, 527, 528 and 5I0 operate. Relays 52? and 528 lock up in a circuit extending from grounded conductor 529, through their windings and lower armatures in parallel, common conductor 536' to grounded battery at the closed contacts of cam. 523. Relay 526, in operating, closes at its lower armature and front contact an obvious operating circuit for nal prepare relay 53| which operates and locks over the upper armature and contact. The prepare relay 526 in operating in response to the operation of key c allows the line circuit to be opened at its upper armature and contact to transmit a spacing signal of sufficient duration to operate slow-acting relay '509 at teletypewriter exchange oiice C to the position opposite to that shown in the drawing. The duration necessary to operate relay 559 is slightly longer than one-sixth second.' Subsequent transmission is not affected by the duration of this spacing signal due to the operation of relay 525 and the normal use of the key for supervision by the operator seems adequate. Relay 526 is restored to the unoperated condition upon the release of key C. The purpose of the slow-acting feature of relay 609 will be hereinafter described. Final prepare relay 53| having operated, and relay 526 having been restored to the unoperated condition, a circuit is closed extending from ground at the lower armature and back contact of relay 526, contact and lower armature `or vrelay 53|, conductor 532,

through the windings of inductance coil 533 and` cord but a splitting relay 502i` associated with the l cord circuit splitting key l2i permits signaling on the answering cord also. Start magnet 534 operatesand `withdraws detent 535 from engagement Awith start-stop cam 524` to permit shaft 5MP-Ato rotate through one revolution only, under the inuence of friction clutch 5|8-A.

Immediately following the rst spacing impulse transmitted over the line circuit due to thev operation 0i relay 525, the line circuit closes with the release oi relay 526 and theline circuit is maintained closed while start magnet 535 is building up suicient current tobeCOmeOperated.

As soon as the shaft 5GB- A begins to operate the line circuit at the contact set in engagement with the rst segment ci cam is opened for the rst spacing signalv to` be transmitted. Subsequently, during the single lrevolution of Vshaft 5i9-A, a series of closures and openings of the line circuit depends on the cuttings of cams 52E! to 522 and these cuttings contr-ol their respectively associated contactsets all' of which are included inthe line circuit. The linecircuit `is traceable from grounded negative battery atthe back contact and outer upper armature of relay i Silit, conductor 532,'through the closed contacts in parallel of the sets respectively vassociated with cams 522, 52i and 525, andthe contacts and upper armatures in parallel of relays 525, `52'! and 525, conductor 53'i, back contact and upperarrnature of relay 505, front contact and upper armature of relay 5H), conductor 5| l, outer right armature and contact of relay M9; conductor 552, through `the upper `and lower windings in series with repeater relay`455, network 454 to ground at the contact and inner left armature of relay 552. The repeater relay 555 in turn repeats the closures and openings of the line circuit, that is, the marking and spacing signals to the receiving circuits at teletypewriter exchange office C. Y

When shaft 5l9-A startsto rotate, `cam 522 opens at its contacts the line circuit to transmit the rst interval of the lll-unit code, the` `open impulse' being transmitted over the closed contact at the upper armature of relay 525. During the second, and extending through to and including the ith interval the impuls-es transmitted are closed, or marking, because the contacts of cam 522 are -closed.- During the sixth interval the contacts of `cam 522 open but because of the operated. conditionof selector relay 521 and the closure oi the contacts at cam 52E, the impulse transmitted is still marking. During the 'seventh interval the contacts of cam 522 remain open and the contacts of cam 52! return to an open position the impulse transmitted is now open. During the eighth interval the contacts of cam 522 close and the contacts of cam. 52E open so that the impulse transmitted is marking. During the ninth interval, the contacts of cam 522 are opened but because of the operated condi- ;,il-Ltion oi selector relay 528 and the closure ofk the 7 uffi contacts of cam520, the impulse transmitted marking. During the tenth interval, the contacts of cam 522 close, those of cam 520 remain open and those of cam y525' open and the impulse transmitted is marking. Also, during the tenth open the holding circuit for relays 53|, 521, 528 and 5i!! whereby the relays release. `The opening of the line circuit due to the release of relay 5H) is not of sufcient duration to affect the receiving end of the line circuit. Therelease of .l interval contacts of cam 523 open to thereby.

relay 5t! releases start magnet 534 so that when the shaft '."aiE--A` completes a single revolution` it will be stopped by detent 535. During the eleventh interval and to the fourteenth interval marking impulses are being transmitted but the u eiective operation oi the receiving signal` distributor had been completed during the ninth nterval and no further description of the operation oi the sending distributor is necessary. The

, transmitted call signal is shown in Fig. 2 ofthe drawings.

Assume that key r is operated by the operator at teletypewriter exchange B to send a recall signal, and the resulting operation is much the same as that described above when the call key c was. assumed to be operated except that selector i relay 528 does not operate and the closure of the contacts of cam 525 during the ninth interval is ineffective. The closing of the contact of cams 522 and 52| respectively are the samer as described above for transmitting the call signal and tiie resulting signal for the fourteen units will be the same except that the ninth interval will be opened instead of closed. The recall signal is ltransmitted as shown in Fig. 2 of the drawings.

Assuming that key d is operated by the ,operatorat teletypewriter exchange orce B to transmit a disconnect signal, the resulting operation is also much `like that described above when call key c was assumed to be operated except that relay 2l does not operate and the closure of the contacts of cam 522i during the sixth interval is ineffective. The closing of the contacts of cams 522 and 525 respectively are the same as described above for transmitting the call signal and the resulting signal for the fourteen units will be the same except that the sixth interval will be openy instead oi closed. The disconnect signal as transmitted is shown in Fig. 2 of the drawings. y

At the incoming end` of the toll circuit iii-"l the line winding of polar relay 552 is connected in the toll circuit at all times. The preliminary opening' of the line circuit due to the operation of the supervisory signaling key c, 1' or d, as`

liereinbeiore described, operates relay 522 to its spacing contact to close an obvious operating circuit for prepare relay Relay 525 is slowacting and is designed to operate on e, signal slightly longer than the letters signal of 'a 60 speed circuit and its purpose is to screen, or protect, the receiving signal distributor from` the normal teletypewriter, or message, signals. lay 559 in operating after a predetermined duration closes an obvious operating circuit for lockup prepare relay 5m. Relay flic, in operating, locks up in a `circuit extending over its right armatureand contact, contact and armature of relay 5H to grounded battery, and over its left.

armature and contact, cicses a circuit extending from grounded battery, armature and leftehand,

or marking, contact of relay to the right When the tollline is subsequently closed7 the circuit, just traced, operates relay SH2. Relay (H2, in operating, locks up through its front contact and right armature to grounded battery at the armature of'relay till and at its left armature and make-before-loreak contact substitutes a circuit to the line relay for the holding circuit for normally operated selecting magnet Git which remains operated. Selecting magnet tis is now prepared tol operate in accordance withV the lll-unit impulses transmitted by the transmitting signal distributor 5M.

The preliminary spacing signal and the marking signal impulse which immediately follows are of suiicient duration to insure theoperation and locking of relay SI2. l

, Selectorv'magnet SH3 in its normal position holds its armature extension i in engagement with cam SI5 and in this position prevents the rotatable shaft @it from rotating under the influence of driving shaft Hill driven by motor GIS, the influence being eifected by friction clutch GIS. In response to the first spacing impulse received by relay tot, the relay operates to its right-hand, or spacing, contact to open the operating circuit for magnet SIS and the armature 6M is released thereby disengaging cam @I3 to permit shaft tit to rotate. Frictionally mount ed on shaft'iii are cams 623 to E23. Integrally formed on each of the cams is a projection. These projections are spaced with respect to each other, angular differences which correspond to the angular differences between the cutting of the segment No. 6 of cam 52i, segments Nos. 'T yand 8 of cam 5222 and segment No. 9 of cam 52D. Inasmuch'as the sixth, seventh, eighth and ninth intervals only of the lli-unit code are effective to operate the supervisory signal lamps B24, 625 and 625 the cams corresponding to the cuttings for the remaining intervals are not necessary and therefore are not employed. Respectively arranged in engageable relation with the projections on cams 629, Sil, 622 and 623 are code bar operating levers 627, 28, 62S and 630. Each operating lever, when operated, initiates a chain of movement through a sword member, a T lever and a code bar somewhat similar to those employed in the printer disclosed in U. S. Patent 1,745,633, supra. ln the particular arrangement shown in Fig. 6 the code bar in being operated to an operated or a non-operated position, accordingly closes or opens contacts in a combination depending'on the supervisory signal that is received. A second armaturey extension 632 is operated in veither of two positions by magnet 6I3 depending on Whether the incoming signal impulse is closed or open and in cooperation with code bar operating levers positions the sword members and finally the code bars. The code bars operate the Contact sets in combination corresponding to intervals Nos. 6, 7, S and 9 in which open or closed impulses depending on whether the signal transmitted is call, recall or disconnect, are received.

Assume as hereinbefore that a call signal is transmitted, that is, a signal in which the first and seventh intervals are open and the second to the sixth and the eighth to the fourteenth are closed, relay fllt in response to the first impulse operates to its right-hand or spacing position. The circuit previously closed when relay SI2 was operated and locked in response to the preliminary open rimpulse and which furnishes the operating current for magnet SIS, is opened at the left-hand contact of relay B08. Magnet GIS releases and the armature extensions 63E and 632 operate, or rotate slightly about pivotal rod 563. Extension G3i disengages cam 6 I5 to thereby permit driven shaft 616 to rotate under the joint influence of friction clutch Elfi, driving shaft Bill and motor Gld. Extension 632 also in being released rotates slightly to make effective the operation of any of the code bar operating levers 627i to 630. The code bar operating levers operate every time they come into engagement with their respectively associated cams, but the operation is ineffective to perform any further function unless the armature extension 632 is in its released position at the time. For each supervisory signal received from teletypewriter exchange oice B start-stop rotatable shaft BIG makes one complete revolution and the operation of the shaft is synchronized with the start-stop shaft 5l9--A at teletypewriter exchange ofce B so that cams S23, 622, 552i and 62@ engage their respectively associated operating levers G30, 529, 628 and 621 during the sixth, seventh, eighth and ninth intervals, respectively. However, only those T levers of those designated 637 to 6&6 are operated by their respectively associated code bar operating levers, when Such operating levers are actuated only while armature extension 632 is in its released position. Should the armature extension E532 remain inits operated position, an actuation of the operating lever would have no effect on the T lever and consequently no effect on the code bars. Respectively arranged in juxtaposition to code barsA 61H to 6M are sets of contact springs (M5 to 648. Each of contact sets 645, 646 and 641 have two spring leaves and contact set 548 has three spring leaves. Also xedly mounted on shaft GIG is cam S49 arranged to close at the end of the revolution of shaft GI, a contact set 550 which has three spring leaves.

The methodl of operation of signal receiving distributor 6013 will now be described. When the call signal is received, the start, or spacing impulse starts shaft SI rotating. The shaft continues to rotate while impulses corresponding to the second and up to and including the sixth interval are being received. These impulses which are marking, reoperate and maintain in an operated position magnet M3. In the sixth interval cam 623 operates lever 630, but inasmuch as extensionrarm 632 is in its operated position cam 623 is ineffective'. When the seventh impulse which in the call signal is spacing, is received magnet SH3 deenergizes to position its extension arm 532 in a released position. At the same time cam 622 corresponding to the seventh interval operates lever 629 which operates and cooperates With the extension arm 632 4in its released position to move code bar 643 to the right so that contact set Si? becomes closed. When the eighth impulse which in the call signal is closed, is received, magnet Sil-l reoperates and moves extension arm 6232 to its operated position. At the same time cam 63! is ineffectively operating lever G28. When the ninth impulse which in the call signal is also closed, is received, magnet 6I3 remains operated and the engagement of cam i with lever $21 is ineffective on the associated Contact set 545.

It is shown then that in response to the call signal only one set of contacts, namely Mill which corresponds to the seventh interval, is operated. Referring to Fig. 10, the circuit operated by the operation of contact set 5137i may be described as being traced from grounded battery, the upper, or normally closed contacts of set 65), conductor contacts of set 641 which, now being operated,

are closed, upper, or normally closed, contacts of set 646, through the winding of relay 65| to ground. Relay 65| operates and at its right armature and contact closes for itself a locking circuit which extends over conductor 653, manually operated switch 656 to grounded battery 655. At its innermost left armature and contact an obvious operating circuit for call lamp 626 is closed. Lamp 626 lights indicating that a call signal is being received. The lamp remains lighted` until the operator opens switch y6513.

During the tenth interval cam 649 operates contact set 656 to close at its lower contacts a .cir-` cuit for operating relay 6| l. `Relay 6|| operates to open the locking circuit for relays 6|| and 6|2 (shown in Fig. 6) which release. The impulses received during the tenth to the fourteenth intervals are marking and have no effect on the signal receiving distributor 664. `At the end of each revolution of shaft 6|6 magnet 6|3 is in its operated position and cam 6|5 is stopped by extension arm 63| in its operatedposition. l

Assuming that a disconnect signal is being Are ceived the impulses received during the first,

sixth and vseventh intervals are open, or spacing,

and those received during, the other intervalsare in response to the first impulse and in response closed, or marking. Shaft 6|6 starts torotate to the sixth and seventh impulses magnet 6|3v releases to position armature extension 632 so that theengagement of cam 623 with lever63|l and cam 622 with lever 629 cause code bars 644 and 663 to move to the right. Code bars 644 and 643 in their operated positions close the circuit shown in Fig. 10 as extending from grounded battery over the upper, or normally closed con.- tacts of set 656, conductors 656, normally closed contacts of set 646, closed contacts vof set 641, lower contacts o set 648 through the winding of relay 652 to ground. Relay 652 operates and at its right armature and contact closes a lock` ing circuit for itself andat'it's middle left armature and contact closes anoperating circuit for disconnect lamp 625. Lamp 625 lightsrand remains lighted until switch 654 is opened. The impulses during the remainingintervals are received, but inasmuch as allare closed, or marking, they have no eiect on the. distributor 664.

tacts of set 656 are closed tov cause the release of relay 6|| and at the end of its revolution shaft 6|6 is stopped by cam 6 |5. l

Assuming that a recall signal is being received the impulses received during the rst, seventh and ninth intervals are open, or spacing, and those received during the other intervals are closed, or marking. Shaft 6|6 starts to rotate in response to the rst impulse and in response to the seventh and ninth impulses magnet 6|3 releases to position armature extension 632, so that the engagement of cam 622 with lever 629, and cam 620 with lever 621 cause code bars 643 and 64| to move to the right. Code bars 643 and 64| in their operated position close the circuit shown in Fig. 10 as extending from grounded battery, over the upper, or normally closed, contacts of set 650, conductor 656, `then over two parallel paths, one extending overthe closed contacts of set 645, through the winding of relay 652 to ground and the other extending over` the closed contacts of set 646, closed contacts of set 641, upper, or normally closed contacts of l set 648, through the winding of relay65l to their outermost left armatures and contacts close an operating circuit for recall lampl1j624. Lamp 624 lights and remains lighted until the operator` opens `switch 654. tervai the release of relays Gi and 6I`2 1s eiec` tive and at theend of its revolution` shaft 6|6 u 10`y is stopped cyarmature extension 63| as herein-` 'ner'ore described.

`Split key 42l when operated closes During the tenth in`v ground. `ltelays 65| and 652 operate and at y -their right armatures and contacts close locking circuits forthemselves to battery 655l and at an obvious operating circuit for splitting relay 568. Relay l 563 operates and at its upper and lower arina-` 15 1i tures and their respectively associated frontcontacts reverses the polarity of the signaling battery so that signaling may be permittedon the` answering cord dit for the purpose of signaling to an operator that may be in some cases connected to a trunk circuit extending to anothery teletypewriter exchange oice instead of to a 1 line circuit as shown in the drawings.

`It is understood that neither sending device 56i nor receiving device 664 are restricted to the l cam 'arrangements shown in the drawings, `but that they may be adapted for other uses by prothe scope of the invention. Thecams are usually arranged in juxtaposition on the shaft as shown in U. S. Patent 1,745,633, supra. Also,

`viding additional cams for making effective additional or other signal unit intervals toacf complish other results, without deviating from( the devices may be equipped with an armature l lever locking wedge such as is shown in Fig. 7

l of U. S. Patent 1,931,672 granted to S. Morton code receiving device responsive to the code combinations sent by said second sending device, and instrumentalities whereby transmission of code combinations from the rst-mentioned sending device is prevented from setting up 'sei lections in the second-mentioned receiving device.

cuits, said last-named means being non-respon-- sive to message code signals.

3. In a communication system, a plurality of branch stations with one of said main stations,

at` opposite ends of said trunk circuit, means whereby said trunk circuit is also adapted to transmit supervisory signals between said main stations, a start-stop device at one of said main stations for transmitting and a start-stop device at the other of said main stations for receiving over said trunk circuit permutation code supervisory signals, slow-acting means in the receivinguend of said trunk circuit for selecting the supervisory signals only and directing said supervisory signals to said start-stop receiving device.

`4. In a communication system, according to claim 3,-wherein said start-stop device for transmitting supervisory signals comprises rotatable cams, a plurality of circuits arranged to be closed in various combinations, circuit closing means controlled by said cams, a source of signaling current for energizing said plurality of circuits,

andl keys for selectively operating said plurality Aof circuits to send from said source a permutation code combination of current impulses peculiar tothe operated key of said keys.

5. In a communication system, according to claim 3, wherein said start-stop device for receiving supervisory signals comprises a plurality of groups of operating levers, rotatable oamsffor successively operating said plurality of groups, groups of operating members respectively controlled by said pluralityof groups and responsive to supervisory signals of a permutation code, circuits operative in various combinations and controlled by said groups of operating members, means for starting and stopping the rotation of said cams, said means being responsive to said supervisory signals to selectively operate said a trunk circuit interconnecting said main sta- I tions for communicating messages between said [main stations and between said branch stations stop receiving device at each of said stations,

.means at each of said switchboards for establishing a connection over said transmission circuit, a plurality of supervisory keys at each of said switchboards, supervisory circuits respectively controlled by said keys, supervisory indicators at each of said switchboards, other circuits for respectively operating said indicators in response to the operation of said start-stop receiving device, a device at the receiving end of said transmission circuit for diierentiating between incoming message signals and incoming supervisory signals received over said transmission circuit by directing said supervisory signals only to said start-stop receiving device, permutation code selecting equipment forming part of said start-stop receiving device responsive to said incoming supervisory signals, circuit closing means responsive to said code selecting equipment in operated position for selecting and operating any one of said other circuits to operate one of said supervisory indicators at the receiving station which corresponds to the supervisory key operated at the transmitting station.

'7. In a printing telegraph exchange system wherein permutation code signals are employed,

a plurality of main stations, a transmission circuit interconnecting said main stations, a manually operated multiposition switchboard at each of said stations, a printer set at each of said -positions arranged to transmit start-stop sigkeys iortransmitting over said transmission circuit permutation oodelsupervisory signals comprising impulses of longer duration than the permutation code signal impulses from said start-stop printer set, a slow-acting device at the receiving end of said transmission circuit responsive to the supervisory signals only, other circuits arranged to be conditioned by the initial operation ofsaid slow-acting device, a selective device responsive to said supervisory signals over said other conditioned circuits, a plurality of signal lamps corresponding in number to said keys at each of said switchboard positions and responsiveto the operation of said selective de- Vice, `the signal lamp operated depending on which of said keys is operated at one oi said switchboard positions.

JAMES M. DESMOND.

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